The present invention generally relates to power hand tools, and more particularly, to power reciprocating tools.
Reciprocating tools that are motor driven, such as saber saws, larger reciprocating saws and the like are usually driven by electric motors that have a rotating output shaft. The rotating motion is translated into reciprocating motion for moving a saw blade or the like in a reciprocating manner.
Reciprocating tools such as jigsaws, saber saws, as well as larger reciprocating saws are typically driven by the rotating output shaft of an electric motor. Such tools have a mechanism that translates rotary motion of the output shaft into reciprocating motion. With the recent emphasis on tool portability, drive motors are increasingly powered by rechargeable battery packs, and even relatively large reciprocating saws are now being powered by such battery packs. Because larger saws are often used for heavy duty jobs, it is important for the run time of the batteries between charges be sufficient that the user does not have to frequently change out and recharge the battery packs while working. Therefore, it is important that the design of such tools contributes to efficient operation.
Typical reciprocating saws have a plunge rod or plunger that is guided in its reciprocating movement by sliding in metal guide bushings. One of the bushings is nearly always located at the very front of the saw and is exposed to dust and debris during operation of the saw. The front bushing typically becomes loaded with dirt and also receives very little grease. Generally, poor lubrication combined with the high coefficiency of friction that sliding bushings typically have results in considerable friction heating and power loss. Sliding plunge rod action in guide bushings typically wastes 50% or more of the power used in operation because of the sliding friction. If the design is one that has counterweights to reduce vibration, such counterweights are also often designed to slide in steel guide bushings. This therefore increases waste of energy and accordingly, most commercially available battery powered reciprocating saws at the present time simply do not have counterweights. This is undesirable because the absence of counterweights substantially increases the vibration that is experienced by a user during operation.